The present invention relates to an engine testing apparatus and further relates to a map preparing method for the engine testing apparatus or a vehicle testing apparatus. More particularly, the invention relates to a novel map preparation method in which learned data (actual machine data) or a learning map for determining a throttle (accelerator) opening degree, which is a target valve for controlling an engine under test or a vehicle under test, is defined as an exponential function or a multiple-degree equation function. Thereby, a peculiar point of the learned data is determined, and the particular point is automatically corrected when preparing the learning map.
The present invention further relates to a novel map preparation method that uses data from a torque curve obtained by varying the throttle valve from a fully closed position to a fully open position while maintaining a constant engine rotation number and that uses data from a torque curve obtained by varying the throttle valve from a fully open position while maintaining a constant engine rotation number. The data is used to prepare a learning map for determining a throttle (accelerator) opening degree which is a target value for controlling an engine under test of a vehicle under test.
A conventional vehicle simulation system carried out on a stage includes a function for learning an engine under test (simply xe2x80x9cenginexe2x80x9d, hereinafter), and a learning map is prepared from the learned data. The engine is controlled based on the learning map.
The learned data is prepared by varying the throttle valve with the engine at an arbitrary rotation number and by storing an output torque (see FIG. 6). FIG. 6 shows a torque curve (actual measured value) obtained by varying the throttle valve from a fully closed position to a fully open position while maintaining the engine rotation number at a constant value. From the torque curve, a torque value is determined at one point with respect to the throttle valve opening degree at a certain engine rotation number (e.g., 2000 rpm).
However, since torque curves A, B, C, D and E of various engine rotation numbers (1000 rpm, 1500 rpm, 2000 rpm, 2500 rpm, 3000 rpm) intersect at a low throttle opening degree in some cases, a peculiar portion is generated in a learning map based on the learned data, and accuracy of the control is deteriorated. For example, a peculiar driving state in which the throttle is closed for acceleration is generated. A first invention has been accomplished in view of the above circumstances, and an object of the first invention is to provide a map preparing method for an engine testing apparatus or a vehicle testing apparatus capable of preventing a peculiar driving state from being generated.
A throttle valve is varied while maintaining an engine at an arbitrary rotation number (e.g., 1500 rpm), and an output torque curve at the arbitrary rotation number is stored. The obtained output curves are determined as learned data 40, and the learning map is prepared based on the learned data 40 (see FIG. 8). Table 1 shows the learning map prepared by the conventional method.
From the learning map of Table 1, an output torque (simply xe2x80x9ctorquexe2x80x9d, hereinafter) is determined at one point with respect to a particular engine rotation number and a particular throttle opening degree. For example, when the target engine rotation number is 1700 rpm and the desired target torque Nm is 30, the throttle opening degree for generating the target torque Nm can be determined from the values 329, 464, 435 and 563 by referring to the learning map of Table 1.
Conventionally, the throttle opening degree is controlled by varying the throttle valve from the fully closed position to the fully opened position, and the throttle opening degree is increased stepwise, for example, at 5% increments. Whenever the throttle opening degree is increased by 5%, it is necessary to wait until the torque is stabilized. The torque value is stored when it is stabilized.
However, when the engine is held at a constant rotation number and the throttle openings are the same, a torque output resulting from a throttle valve operated in the opening direction differs from a torque output resulting from the throttle valve operated in the closing direction. On the other hand, the conventional learned data can be obtained only when the throttle valve is fixed and the torque is stabilized as described above. Therefore, it is not possible to obtain a learning map corresponding to a variation in speed during a running speed pattern of a driving mode.
For example, it can be found from FIG. 11 that actual vehicle data 38, which exhibits variations in throttle opening degree of an actual vehicle running on a chassis dynamo based on a running speed pattern I of a driving mode, intersects data 39, which is data simulated according to the conventional method. In FIG. 11, the pattern I is constituted by constant speed straight lines f, h, k, o, r, w, x, acceleration straight lines g, j, l, q and deceleration straight lines i, p, s and u.
That is, from FIG. 11, the following points can be found:
(1) For example, with respect to acceleration straight line j, data 38 does not coincide with data 39. That is, since an output torque with respect to a throttle opening degree operated while referring to the learning map and a torque necessary for acceleration do not coincide with each other, data 39 is deviated higher than data 38 in the first half. In order to correct the deviation of vehicle speed, data 39 is deviated lower than the data 38 in the latter half.
(2) A reversal exists in the vertical relation between data 38 and data 39 in the case of the acceleration straight line j and the vertical relation between data 38 and data 39 in the case of the deceleration straight line p.
(3) The same phenomenon exists in the acceleration straight line g and the deceleration straight line s.
In this manner, since the accuracy of the simulation is poor, it is difficult to accurately drive an engine with respect to the running speed pattern I of the driving mode.
A second invention has been accomplished in view of the above circumstances, and an object of the second invention is to provide a map preparing method for an engine testing apparatus or a vehicle testing apparatus capable of enhancing the simulation accuracy.
To verify the performance of an automobile engine, there exists an engine testing apparatus comprising a dynamometer connected to an output section of an engine which is to be tested, a dynamo controller for controlling the dynamometer, and an actuator for controlling a throttle opening degree of the engine under test. The engine testing apparatus controls the dynamo controller and the actuator to adjust the output of the engine under test.
In the conventional engine testing apparatus, the rotation of the dynamometer is controlled by the dynamo controller, the throttle valve of the engine under test is controlled and operated, and the output torque of the engine under test is controlled, thereby simulating the actual vehicle running.
However, the conventional engine testing apparatus does not have a function for controlling the temperature of the peripheral portions of the engine under test such as engine cooling water temperature, fuel temperature, air intake temperature, exhaust gas temperature and lubricant temperature. Therefore, the temperature environment of an actual vehicle can not be reproduced, and engine behavior similar to the actual vehicle can not be obtained. Thus, high simulation accuracy can not be obtained.
A third invention has been accomplished in view of the above circumstances. The object of the third invention is to provide an engine testing apparatus capable of simulating an actual running vehicle with high accuracy.
The first invention comprises varying a throttle valve from the fully closed position to the fully open position while maintaining an engine at a constant rotation, carrying out an operation of storing an output torque using at least three different engine rotation numbers, determining torque curves for each of the engine rotation numbers as actual machine data, and preparing a map based on the actual machine date. The preparation of the map is characterized by describing each of the torque curves on the same X-Y plane when a map is prepared based on the actual machine data, converting actual machine data function for describing torque approximation curves with respect to throttle opening degrees (X axis) on the same X-Y plane while making approximations to the torque curves, determining the existence of intersecting torque approximation curves, and automatically correcting the torque approximation curve which is determined peculiar such that a value of a y-component of the peculiar torque approximation curve assumes a median value of the y-component of each of the vertically adjacent torque approximation curves.
The second invention comprises calculating an average value of throttle valve operating speed from variation of the throttle valve operation speed, determining the average value of the throttle valve operating speed obtained by the calculation as a representative value corresponding to the throttle valve operating speed in a driving mode, operating the throttle valve in a state where the engine rotation number is made constant by the representative value, describing the torque curves with a plurality of engine rotation numbers, and preparing a map for determining the throttle opening degree based on the obtained torque curves.
According to another aspect of the second invention, a map preparing method is provided. The map preparing method is used for an engine testing apparatus or a vehicle testing apparatus. The map preparing method comprises calculating an average value of the throttle valve opening direction and an average value of the throttle valve closing direction from variations of the throttle valve operation speed, determining the average value of the throttle valve opening direction obtained by the calculation as a representative value corresponding to the throttle valve operating in the throttle valve opening direction in a driving mode, operating the throttle valve in the opening direction in a state where the engine rotation number is held constant by the representative value and describing the torque curves with a plurality of different engine rotation numbers, and preparing a map of the throttle valve opening direction based on the obtained torque curves, determining the average value of the throttle valve in the throttle valve closing direction obtained by the calculation as a representative value corresponding to the throttle valve operating in the throttle valve closing direction in a driving mode, operating the throttle valve in the closing direction in a state where the engine rotation number is held constant by the representative value and describing the torque curves with a plurality of different engine rotation numbers, and preparing a map in the throttle valve closing direction based on the obtained torque curves.
According to the third invention, an engine testing apparatus is provided. The engine testing apparatus comprises a dynamometer connected to an output section of an engine which is to be tested, a dynamo controller for controlling the dynamometer, and an actuator for controlling a throttle opening degree of the engine under test. The dynamo controller and the actuator are controlled to adjust an output of the engine under test, wherein commands based on a temperature pattern obtained from temperature data of various portions of the engine while running an actual vehicle in accordance with a running pattern on a chassis dynamo from an apparatus for controlling the entire apparatus to various temperature adjusting devices provided around the engine under test.
An apparatus for controlling the engine testing apparatus outputs, for example, commands based on the temperature pattern obtained from temperature data of various portions of the actually running engine in accordance with the running pattern on the chassis dynamo to various temperature adjusting devices provided around the engine under test. Thus, it possible to reproduce the temperature environment of the actual vehicle and obtain an engine behavior similar to the actual vehicle. Therefore, high simulation accuracy can be obtained.
The commands based on the temperature pattern may be based on a virtual vehicle simulation. In this case, it is possible to arbitrarily carry out the simulation of a virtual vehicle by adding various conditions.